Overclocking Guide - Intel

by NoAffinity
07-18-2004
Discuss this article.

Firstly, it is currently the mostly widely used word that does not appear in the English dictionary. Secondly, it is causing hardware (particularly CPU, RAM, motherboard and video card) to operate above and beyond rated specs. We need to establish the idea of rated specs as being the level to which a particular piece of hardware is expected to, has been tested to and is warranted to perform. What this equates to in the real world (and when I say real world, I mean that driven by capital venture) is a certain price tag for a certain level of expected performance. We, as overclockers, strive to determine not what we’ve been told our hardware can do, but what can really be gotten out of it.

Some quick basics, as they pertain to Intel systems

1) Intel overclocking is achieved via the front side bus, or system bus. Depending on your system, it can be noted as FSB, CPU frequency, CPU speed, or something similar in the BIOS. Upping FSB will increase the system bus.

2) Intel CPU’s are “quad pumped” internally (Intel’s word for the process). What this means, I couldn’t tell you exactly…something along the lines of frequency multiplication. What this equates to for the end user is the front side bus will be ¼ the CPU’s advertised bus speed. If you have a 400 mhz FSB CPU, in BIOS it will be 100 mhz stock FSB speed. If you have a 533 mhz FSB CPU, in BIOS it will be 133 mhz stock FSB speed. Etc etc.

3) Conversely, DDR RAM transmits data on both sides of a tactical signal, effectively performing two functions per single clock cycle. That is why it’s referred to as Double Data Rate RAM. Some systems’ BIOS list actual DDR speed in BIOS (i.e. 333 mhz, 400 mhz, etc), while some list system bus speed (which is ½ of the RAM’s rated speed, i.e. 166 mhz, 200 mhz).

4) On Intel systems, best performance is achieved through highest possible stable operation in synchronous (1:1) CPU:RAM operation. The higher the FSB in 1:1, the better performance. The only exception may be if you have severely limiting RAM and a CPU that is an excellent overclocker. That is up to you to determine, tho. Does a 5:4 divider at a super high CPU clock offer better performance than half the FSB in 1:1? Well then, stick with 5:4. At the same time, running RAM faster than the CPU offers absolutely no performance gains (the CPU is doing the processing, RAM merely receives data as it is fed to it...). I don’t know why motherboard manufacturers even offer dividers to run RAM faster than the CPU, but they do. So, please, for my sake, don’t go setting your CPU bus speed to 133 mhz and DRAM frequency to 200 mhz (or 400 mhz, depending on how your BIOS lists it).

5) Intel multipliers are locked. FSB is the only way to overclock an Intel system. The locking of the multiplier is achieved via a laser cut on the CPU’s die. The channels for multipliers, other than the intended one, are essentially “blocked” from being accessible via BIOS due to this laser cut. The only exception to this rule is engineer’s sample processors. They are rare and not something you will ever purchase from your average retailer.

6) Proprietary systems do not overclock. Dell, HP, Gateway and Intel-manufactured boards all have their front side buses locked.

7) Familiarize yourself with the CMOS jumper. Once you start OC’ing, if you push a little too far and your system won’t boot at all, just clear CMOS and start over.

8) While this guide is intended to start you on your way to overclocking your current setup, keep in mind that upgrades will help achieve higher overclocks. Without saying right off the bat that you need to go out and purchase this or that, good cooling and a solid PSU are generally recommended for protecting your investment in a stressful operating environment.

Basic BIOS 101

Okay, now that we’ve established some basic ground rules, let’s get down to business. First and foremost, get into the BIOS. This is done by pressing the ‘DEL’ button at system startup. Once you are in the simplistic blue screen with all the wonderful (and possibly confusing, if this is your first time or you are still new to OC’ing), take a look around. Familiarize yourself. Read all the listings, and check out their available options. It may not all make sense to you, but it’s good to know where everything is. Something you can’t possibly imagine that you would ever need to change today may come in handy tomorrow.

Now then, let’s establish some basic settings that will apply to all BIOS’s and all overclocking. They may not appear exactly as listed, but it will be something very very similar:

Spread Spectrum– ‘disabled’
PCI/AGP/SATA – ‘fixed’ or ‘locked’ or ‘33/66/100’
Stop unused PCI clock – ‘enabled’

Furthermore, ensure that your “Initial Display Adapter” is set accordingly (i.e. PCI or AGP, depending on your video card’s interface), and don’t hesitate to disable anything under “Integrated Peripherals” that you are not using (i.e. Serial Port, Parallel port, onboard audio, etc). This will free up unused resources.

Overclock

I will start with some general recommendations/knowledge, and finish up with the how-to.

Okay, so you’re in BIOS, you’ve made a few minor tweaks, as recommended. Now get to the menu that contains CPU freq., CPU voltage, Spread Spectrum, AGP voltage, etc etc. Your stock bus speed is already set. If it is grayed out, find the option to change from ‘auto’ to ‘manual’ that will give you access to such things as CPU freq., CPU voltage, etc. RAM speed may be listed in a different menu (normally Advanced Chipset
Features), so first things first, make sure it is set accordingly. If you have RAM that is rated to run on a faster bus than your CPU (i.e. a 533 mhz FSB CPU in conjunction with DDR400 RAM), awesome, you have headroom. You still want to set it to 1:1 operation, as this will offer the best performance. The exception, of course, is if your CPU is rated to run on a faster bus then your RAM. If this is the case, then set RAM speed accordingly.

Once you start overclocking, there will be three general limiting factors: vcore, RAM and heat. For Northwood chips keep your load temps under 55C and vcore no greater than 1.7v (whichever comes first, let that be your limiting factor). For Prescott chips, 65C load temps and 1.525v should be your upper limits.

Now that we have all that established, the general principles have been outlined and you have a general knowledge of the terms, what you will see in BIOS, and the basic troubleshooting principles for finding your system’s highest stable operating parameters, let’s get going with the actual procedure!!!! Start by upping CPU frequency (CPU speed, FSB) 3-5 mhz at a time. Again, this single setting will affect your entire system bus. Once increasing FSB, boot into your operating system. If you have reached the desktop successfully, then go back to BIOS and repeat until you experience instability (usually in the form of reboots or system lock-ups). Once you hit a wall, up vcore one notch. If this doesn’t help, up it another notch (see above paragraph for vcore/heat limitations which should always be adhered to). If upping vcore doesn’t seem to be helping, then you can loosen your RAM’s timings (the higher the number, the looser the timing; so, 3-8-4-4 is the absolute loosest timings you can achieve on DDR RAM. If you see no gains, lower RAM speed (or CPU:RAM ratio/divider). Once you reach the point where you are not exceeding the RAM’s rated operating speeds (or are sure it will run at the current speed), and you are at the upper limit of either CPU temps or vcore, then you have found your CPU’s highest stable overclock. Congratulations! Once this has been achieved, and you are at the desktop at what appears to be a stable level of operation, I would strongly recommend testing stability with memtest (strictly for RAM), Prime95 (good all-around tester which offers torture tests for CPU alone, RAM alone, and overall system stressing), and 3dMark01 (good all around CPU/RAM/VC tester). Hopefully you have achieved an acceptable (in your mind) overclock. We expect some screen shots!

Granted there’s a lot of info here, and it may not all make sense immediately. Don’t hesitate to ask questions, start a thread, rely on the guys that have been at it for a while. We were all newbs once, and I personally have fried more than a couple pieces of hardware (some expected, some not expected). The bottom line, have fun, keep it within the parameters outlined, and if you see something that doesn’t look right (like greatly fluctuating FSB frequency), then shut your comp down, clear CMOS and try again.

That's about it, folks. Hopefully this is helpful to some if not many, and if I forgot anything or something needs to be amended, let me know.